Nghiên cứu nâng cao cường độ chịu kéo khi uốn và khả năng chống mài mòn của bê tông cát mịn đối với mặt đường bê tông xi măng tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF CONSTRUCTION VIETNAM INSTITUTE OF BUILDING SCIENCE AND TECHONOLOGY NGO VAN TOAN RESEARCH OF IMPROVEMENT OF TENSILE STRENGTH IN BENDING AND ABRASION RESISTANCE OF FINE SAND CONCRETE FOR CEMENT CONCRETE PAVEMENT Specialization: Materials engineering Code : 9520309 SUMMARY OF DOCTORAL THESIS HA NOI-2019 THE DISSERTATION IS COMPLETED AT: VIETNAM INSTITUTE FOR BUILDING SCIENCE AND TECHONOLOGY Academic supervisor: Dr HOANG MINH DUC INSTITUTE OF CONCRETE TECHONOLOGY - VIETNAM INSTITUTE FOR BUILDING SCIENCE AND TECHONOLOGY Dr NGUYEN NAM THANG VIETNAM INSTITUTE FOR BUILDING SCIENCE AND TECHONOLOGY Reviewer 1: A/Prof Dr Vu Dinh Dau Reviewer 2: A/Prof Dr Nguyen Duy Hieu Reviewer 3: Dr Nguyen Duc Thang This dissertation will be defended by Academy Doctoral Examination Boar at Institute of Building Science and Techonology, 81 Tran Cung street, Nghia Tan, Cau Giay District, Ha Noi at …… on the day of 2019 The dissertation may be read at: - National Library of Vietnam - Library of Vietnam Institute of Building Science and Techonology LIST OF PUBLISHED SCIENTIFIC WORKS OF AUTHOR RELATED TO THE DISSERTATION Hoang Minh Duc, Ngo Van Toan "Study the effect of mortar residual coefficient on the properties of concrete and fine sand concrete mixture using as cement concrete pavement", Construction Magazine - Ministry of Construction No 11, 2018 Hoang Minh Duc, Ngo Van Toan "The impact of limestone grit on the abrasion and shrinkage of fine sand concrete on cement concrete pavement", Journal of Transport - Ministry of Transport, No 12, 2018 Hoang Minh Duc, Ngo Van Toan "Study on improving tensile strength in bending and abrasion resistance of fine sand concrete using to make cement concrete roads", Transport Magazine - Ministry of Transport, No 6, 2019 4.Hoang Minh Duc, Nguyen Nam Thang, Ngo Van Toan "Selecting concrete components using fine sand according to tensile strength when bending", Journal of Construction Science and Technology - Institute of Construction Science and Technology, No 2, 2019 Ngo VanToan, Hoang Minh Duc "Selection of concrete components using fine sand and stone grit mixing according to tensile strength when bending for cement concrete pavement", Transport Magazine - Ministry of Transport, No 7, 2019 INTRODUCTION Abstract The more and more developed the country, the greater the need for travel, that requires the construction of a higher and higher traffic system, resulting in an increasing demand for materials used in the concrete industry This leads to the current general trend of making the best use of locally available aggregate materials in concrete production to reduce construction costs At present, the raw sand source in the country is increasingly scarce while the fine sand source has very large reserves distributed in many regions across the country that are less interested in using in the concrete industry To meet the needs of materials for construction works, transportation besides the traditional materials such as raw sand, it is impossible not to mention the fine material used for cement concrete in general, especially concrete roads Prior to this fact, the topic "Research of improvement of tensile strength in bending and abrasion resistance of fine sand concrete for cement concrete pavement" was conducted, contributing to demonstrate the ability to use fine sand sources instead of raw sand to make concrete used for cement concrete pavement and evaluate the feasibility of applying this type of concrete to transportation and construction works, construction, irrigation in our country Rationale of the Study Raw sand reserves are limited, unevenly distributed, while fine sand is available in many localities across the country that can be used to make cement concrete for road surface However, due to the size modulus of the small fine sand, in the past, standards and technical guidelines used only fine sand for concrete with compressive strength less than 30MPa and proportional correlation with compressive strength above tensile strength when bending to reach level (tensile strength when bending only reaches 4.0MPa), abrasion is only 5.0MPa, compressive strength over 40MPa), but does not reduce the abrasion of concrete to < 0.3g/cm2 Beside, concrete using fine sand is also dehydrated, splitting mortar, softening stronger than concrete using coarse sand and concrete using fine sand with crushed stone Therefore, this type of concrete can only be used as a concrete pavement of - level roads or yards when appropriate technological measures are applied to limit cracking of concrete surfaces Chapter OVERVIEW OF RESEARCH AND USING OF FINE SAND CONCRETE 1.1 Overview of research situation and using of fine sand concrete 1.1.1 Classification and technical requirements for sand as aggregate for concrete In the Russian Federation, according to the GOST 8736-93 standards; GOST 26633-91 and "Instructions for use of fine sand and very fine sand for concrete pavement and airport" In the United States, applying the AASHTO M6-93 standard; ASTM C33-03 In Vietnam, according to Vietnam standard TCVN 7570: 2006 "Aggregates for concrete and mortar - Technical requirements"; According to Decision 778/1998/QD-BXD, "Technical instructions for selecting concrete components of all kinds" and according to TCXD 127:1985 standard, "Fine sand for making concrete and construction mortar - Instructions for use" Standards of countries have not agreed on the scope of application of fine sand, generally, all standards stipulate that sand is considered fine sand when the modulus of magnitude is less than (Mdl < 2) 1.1.2 The situation of research and use of fine sand concrete in the world In the world, the study and use of fine sand to make cement concrete mainly in two main directions: a) Using fine sand as aggregate in the manufacture of smallgrained concrete (also called sand concrete - concrete without large aggregates); b) Use fine sand instead of all or part of the rough sand (M dl> 2), in ordinary concrete (with large aggregate)  Using fine sand as aggregate in manufacturing small-grained concrete, which has been studied and used by many countries in the world: as in the former Soviet Union; Russian Federation today; Algieri and France However, the research orientation of the thesis is to use fine sand instead of all raw sand in manufacturing and producing ordinary concrete Therefore, it is necessary to focus on the studies of countries in the world in the following direction:  Using fine sand to replace all or part of raw sand (M dl>2), in conventional concrete, these studies have been researched and used by many countries in the world: in the Soviet Union (former) Research on fine sand used in concrete has been carried out quite early, especially for hydraulic concrete Until the year of 1950s of the twentieth century, fine sand was standardized in "Technical guidelines for using fine sand in hydraulic concrete" In the year of 1970 of the twentieth century, Do-nhi-ep fine sand and Bar-khan was applied to concrete in a number of hydraulic construction projects A number of research works by Ki-ri-en-co, S.tonnhi-cop and Gu-Ba have also been published By the year of 1980s of the twentieth century, it was studied to use sand from the Enisei river to build SayanoShushenskaia hydroelectricity Also during this period, one of the areas where fine sand was widely used was in the transport, especially the manufacture of concrete for roads and airports, which was done in the research of Research on road construction) is considered as the basis for preparing the "Guidelines for the use of fine sand in cement concrete for roads and airport pavements" and "Guidance for the use of low-aggregate concrete of large quantities using fine sand in building pavement of cars and airports” In China since the year of 1965 of the twentieth century, fine sand was also studied and put into use in concrete, this is mentioned in the BGY Regulation 19-65, allows the use of sand with a module size greater than 0.7 to make concrete In 2009, the DuBai City project in the United Arab Emirates used cement concrete that uses fine sand of (300÷400) kg per cubic meter of concrete, resulting in compressive strength of the value of 45MPa Fine sand may be river sand but fine sand can also be desert sand, so in the Middle East countries, many studies have been conducted with desert fine sand of high fineness, moderately fine sand from 0.45 to 0.88 In China, the Tenggeli and Maowusu desert sands with modules of 0.334 and 0.194 magnitudes have been studied for use in mortar and concrete In Australia, research on the use of desert fine sand is also of interest During the study of river sand used in concrete, Kim et al Studied cracked properties of concrete using crushed sand from limestone in Korea, the results showed that when used in combination with sand grinding from limestone and sand has improved the intensity of concrete In the study of author XieZhi-Hua, took advantage of sand and crushed powder from seashells to make cement concrete, the results showed that strength The degree of concrete is also improved In Asia, research by ‟RSNaidu, M Zai University Malaysia, Malaysia and SE Ang, Open University Kebangsaan Malaysia ” studied the compressive strength of concrete using fine sand, crushed sand and mineral additives, the results showed that when replacing 20% of fine sand by sand grinding dust in concrete, compressive strength of concrete is lower than when using fine sand alone, when using 10% fly ash to replace adhesives in concrete components, the compressive strength of concrete is increased Concrete using dust grit sand combined with 10% silica fume instead of the binder component shows that the strength of concrete reaches the highest value 1.1.3 The situation of research and use of fine sand concrete in Vietnam The use of fine sand for concrete in Vietnam has been studied for a long time, such as the topic ‟Using black sand of the Red River to produce concrete (CCA)" – Doc Nguyen Van and Lan Hoang Phu chaired and reported the Conference of Concrete throughout the North - 1967 ” By the 70s of the twentieth century, the Institute of Water Science Research and the Institute of Construction Science and Technology had studied and applied fine sand concrete with the compressive strength  30 MPa for a number of hydraulic works and civil construction The study on “using fine sand for concrete and construction mortar” - Nguyen Manh Kiem and Duong Duc Tin, has been conducted with a number of different fine sand types in the Northern region (Cao Lang, Vinh Phu, Ha Nam Ninh, Thai Binh, Hanoi) Types of sand used in the study (Mdl=0.47÷1.97), compared with concrete using rough sand (Mdl= 2.20÷2.26) with the same compressive strength and tensile strength, prismatic strength, elastic modulus, bonding strength between concrete and reinforcement, water absorption, softening coefficient and contraction of concrete using fine fine sand equivalent to raw sand The abrasion resistance of concrete using fine sand is inferior to that of concrete using raw sand The topic also mentioned the use of plasticizers as a cement saving measure However, these are just initial studies, the role of plasticizers when using fine sand has not been clearly defined By the 90s of the twentieth century, there were studies using fine sand of the Red River (Mdl=1.1÷1.72) in intermittent concrete mixtures with intermittent levels of sand loam different from (19÷40)%, the ratio of N/X from (0.40÷0.55), the amount of cement used (233 ÷ 526) kg/m3, indicating that the slump of concrete mixes may vary from (0 ÷ 18) cm, the intensity reaches from (28÷50)MPa In 2005, studies using fine sand to manufacture high-strength concrete at Hanoi University of Construction were conducted with an additive system including mineral admixtures and superplasticisers and fine sand (Mdl=1.08) used in research; compressive strength of concrete to achieve values up to 98MPa (sample 10x10x10cm) In 2006, Vung Tau and Binh Thuan sands with modules of 0.95 and 1.31 respectively and NaCl content of about 0.06% are studied to make cement concrete for highways construction The research results show that the fine sand in the sea can be used to make cement concrete for the construction of high-grade pavement, the surface of low-grade automobile pavement and the pavement of rural roads in suburban sea provinces In 2006, a study on using Red river black sand made low strength concrete, proposed fine sand (M dl=1.1) used to make concrete with required strength over 10MPa, the authors also propose to use roller compaction method for low strength concrete construction using fine sand By 2010, there was a study on the use of fine sand and the mixture of rice husk ashslag ash additives to produce high strength concrete, resulting in the compressive strength of concrete at the age of 28 days gained from (67÷80) MPa, chloride ion permeability level is very low In 2012, there was a study on the use of Song Hong black sand (Mdl=1.0;1.5;2.0) and the workability of D3, D4 to produce 40MPa concrete for local constructions in Hanoi In 2013, fine sand in the Mekong Delta (Mdl=1.21) was studied in concrete fabrication with a ratio of sand to the aggregate of 0.34 to 0.40 The results show that when using fine sand, the decrease is about (23÷25)% but the decrease level over time is less, compressive strength decreases from (9÷15)% The elasticity of the modulus is reduced (5÷7)% compared to when using raw sand (Mdl=2.71) Fine sand concrete has a higher shrinkage than raw sand concrete at age 60 days Fine sand concrete has higher water absorption and chloride permeability than raw sand concrete, but the waterproofing is equivalent (declining at a high N/X ratio) In 2010, there was a study of mechanical properties and applicability of sand concrete for building roads, the author used sand (Mdl=1.73) used for sand concrete, achieving the value of the intensity of compressive strength of concrete at the age of 28 days from (30÷40) MPa In the field of manufacturing concrete products, fine sand is also commonly used At Song Day Construction Material Joint Stock Company, Hong river sand (Mdl=1.2÷1.5) has been used to produce culverts, manholes, box culverts At Song Day Joint Stock Company - Hong Ha Petroleum also used fine Hong River fine sand (Mdl=1,5) to produce autoclaved aerated concrete block (AAC) of compressive strength and  Regarding research on improving tensile strength in bending and abrasion resistance for fine sand concrete, there have been some research works The outstanding contents and rules can be drawn from these studies: fine sand concrete follows the general rules with cement concrete The influence of fine sand on the properties of concrete and concrete mixtures is reflected in changing the amount of water used, the workability and the strength of concrete However, the characteristics and the degree of influence depend on the characteristics of the sand as well as the use of concrete On the other hand, in the standards and technical guidelines of some countries around the world, the use of fine sand is still in the open trend, so if appropriate and optimal technology measures are used component of concrete, concrete can be made using fine sand to meet the technical requirements and the amount of cement equivalent to the concrete using coarse  Summary of studies in the world and in Vietnam, it can be seen that fine sand was initially used to make cement concrete roads at all levels In order to develop and expand these applications in practice, especially in the context of Vietnam, more in-depth studies are needed as well as further clarification of one of the points of particular interest, when using fine sand, there are some disadvantages such as bending strength in bending and abrasion resistance of concrete using fine sand lower than coarse sand Therefore, the study to improve the tensile strength of bending and abrasion resistance of concrete using fine sand equivalent to coarse sand, meeting technical requirements for cement concrete pavement for roads at all levels is very necessary and has a scientific basis The current surface of cement concrete roads is usually constructed using roller-compacted and vibratory technology, in the conditions in Vietnam, especially in remote areas, Northwest areas with complex terrain, the work vibratory technology can be considered more reasonable Therefore, the thesis focuses on construction methods based on normal vibration technology 1.2 Characteristics and properties of cement concrete for road construction Technological characteristics of cement-concrete for road construction are cast in situ place concrete without cased beam and solidified in natural conditions Concrete cast, compaction and finishing are carried out by means of a specialized apparatus which are suitable for the construction of relatively dry concrete mixtures Strength is the most important characteristic of cement concrete for road construction, evaluated by two criteria: tensile strength during bending and compressive strength in which tensile strength when bending is the main criterion The compressive strength used to evaluate the wear resistance of surface concrete Abrasion is also a major indicator of concrete for roads Stability and deformation properties are also an important characteristic of concrete for roads Elastic modulus of concrete characterizes the ability of concrete to deform under the effect of a load Shrinkage of concrete is an important property of concrete for making roads 1.3 Characteristics, properties and technical requirements for concrete pavement surface 1.3.1 Characteristics and properties for cement concrete pavement Cement concrete pavement is a high-grade hard pavement The surface layer is a cement concrete with very high stiffness, the computational model is on the elastic floor (soil and road foundations) The main strength reinforcement of the sheet is tensile strength during bending 1.3.2 Technical requirements for cement concrete pavement According to standard 22TCN 223-95; According to Article 5.2.a, Circular No.12/2013/TT-BGTVT; According to the Minister of Transport's Decision No 1951/QD-BGTVT of August 17, 2012: a) Tensile strength in bending: with cement concrete surface of highways, grades I and II less than 5.0MPa, with pavements of cement concrete grade III or lower not less than 4.5MPa b) Abrasion: with the cement-concrete pavement of expressways, I,II,III lever not bigger than 0.3g/cm2, with pavements of cement concrete IV lever or lower not exceeding 0.6g/cm2 1.4 The scientific basis of the dissertation As analyzed above, the disadvantage of fine sand concrete is that it has compressive strength, tensile strength when bending lower than coarse sand concrete (10÷15)% when using the same amount of cement and have the same construction slump In addition, fine sand concrete has low abrasion resistance, the abrasion is usually from (0.3÷0.6) g/cm2 compared to the value (